Jessica L. Moore

Clonal fate mapping quantifies the number of haematopoietic stem cells that arise during development

Haematopoietic stem cells (HSCs) arise in the developing aorta during embryogenesis. The number of HSC clones born has been estimated through transplantation, but experimental approaches to assess the absolute number of forming HSCs in a native setting have remained challenging. Here, we applied single-cell and clonal analysis of HSCs in zebrafish to quantify developing HSCs. Targeting creERT2 in developing cd41:eGFP+ HSCs enabled long-term assessment of their blood contribution. We also applied the Brainbow-based multicolour Zebrabow system with drl:creERT2 that is active in early haematopoiesis to induce heritable colour barcoding unique to each HSC and its progeny. Our findings reveal that approximately 21 HSC clones exist prior to HSC emergence and 30 clones are present during peak production from aortic endothelium. Our methods further reveal that stress haematopoiesis, including sublethal irradiation and transplantation, reduces clonal diversity. Our findings provide quantitative insights into the early clonal events that regulate haematopoietic development.

CXCR1 remodels the vascular niche to promote hematopoietic stem and progenitor cell engraftment

The microenvironment is an important regulator of hematopoietic stem and progenitor cell (HSPC) biology. Recent advances marking fluorescent HSPCs have allowed exquisite visualization of HSPCs in the caudal hematopoietic tissue (CHT) of the developing zebrafish. Here, we show that the chemokine cxcl8 and its receptor, cxcr1, are expressed by zebrafish endothelial cells, and we identify cxcl8/cxcr1 signaling as a positive regulator of HSPC colonization. Single-cell tracking experiments demonstrated that this is a result of increases in HSPC–endothelial cell “cuddling,” HSPC residency time within the CHT, and HSPC mitotic rate. Enhanced cxcl8/cxcr1 signaling was associated with an increase in the volume of the CHT and induction of cxcl12a expression. Finally, using parabiotic zebrafish, we show that cxcr1 acts HSPC nonautonomously to improve the efficiency of donor HSPC engraftment. This work identifies a mechanism by which the hematopoietic niche remodels to promote HSPC engraftment and suggests that cxcl8/cxcr1 signaling is a potential therapeutic target in patients undergoing hematopoietic stem cell transplantation.

Sex Trafficking of Minors

Sex trafficking is an increasingly recognized global health crisis affecting every country and region in the world. Domestic minor sex trafficking is a subset of commercial sexual exploitation of children, defined as engagement of minors (<18 years of age) in sexual acts for items of value (eg, food, shelter, drugs, money) involving children victimized within US borders. These involved youth are at risk for serious immediate and long-term physical and mental health consequences. Continued efforts are needed to improve preventive efforts, identification, screening, appropriate interventions, and subsequent resource provision for victimized and high-risk youth.

Trafficking Experiences and Psychosocial Features of Domestic Minor Sex Trafficking Victims

Domestic minor sex trafficking (DMST) is an increasingly recognized traumatic crime premised upon the control, abuse, and exploitation of youth. By definition, DMST is the “recruitment, harboring, transportation, provision, or obtaining of a person for the purpose of a commercial sex act” within domestic borders, in which the person is a U.S. citizen or lawful permanent resident under the age of 18 years. The present study described the demographics, psychosocial features, and trafficking experiences (e.g., environments of recruitment, relationship to trafficker, solicitation) of DMST victims. A total of 25 medical records of patients under the age of 18 who disclosed their involvement in DMST to medical providers between August 1, 2013, and November 30, 2015, were retrospectively reviewed. The majority of patients were female, and the mean age was 15.4 years old. Most patients lived at home and/or were accompanied at the evaluation by a parent/guardian. High rates of alcohol or substance use/abuse (92%), being placed in a group home or child protective services (CPS) custody (28%), a history of runaway behavior (60%), and/or exposure to other child maltreatment (88%) were identified. Our data indicated variation in reported trafficking experiences; however, patients commonly reported an established relationship with their trafficker (60%) and recruitment occurred primarily as a result of financial motivation (52%). Patients were prevalently recruited in settings where there were face-to-face interactions (56%), whereas the solicitation of sex-buyers occurred primarily online (92%). Victims who disclosed involvement in DMST had complicated psychosocial histories that may have rendered them susceptible to their exploitation, and reported a variety of DMST experiences perpetuated by traffickers. Although preliminary in nature, this study provided empirical evidence of the predisposing factors, motivations, and experiences of victimized youth uniquely from the perspective of patients who sought medical care.

The Prevalence of Rib Fractures Incidentally Identified by Chest Radiograph among Infants and Toddlers

Objectives To determine the prevalence of incidental rib fractures identified by chest radiograph (CXR) obtained for indications unrelated to accidental trauma or nonaccidental trauma (NAT), and describe the histories associated with cases of incidental rib fractures and their proposed etiologies. It is hypothesized that incidental rib fractures are rare and alternative explanations for rib fractures occasionally used in a medico‐legal context such as minor accidental trauma, undiagnosed medical conditions, and transient metabolic bone disturbances are unlikely to be the etiology of incidental rib fractures. Study design A retrospective chart review of sequential CXRs of children ages 0 to <2 years was conducted from January 1, 2011 to October 31, 2016. CXRs were obtained in the emergency department, general pediatric or intensive care units, or outpatient pediatric clinics. Data collected included demographics, CXR indication and findings, history of cardiopulmonary resuscitation, laboratory and additional imaging results, and incidental rib fracture descriptions and proposed etiologies. Results A total of 7530 patients underwent 9720 CXRs associated with unique clinical encounters. Five CXRs had incidental rib fractures identified, making the prevalence of CXRs with incidental rib fractures in this cohort <0.1%. Of 5 identified incidental cases, mean age was 3.6 months, 3 were concerning for NAT, 1 was confirmed NAT, and 1 had radiographic findings consistent with osteopenia of prematurity. Conclusions Identification of incidental rib fracture on CXR is rare. When detected in the absence of corresponding trauma history and/or objective laboratory or radiographic metabolic abnormalities, work‐up for NAT should be pursued.

Domestic Minor Sex Trafficking

Commercial sexual exploitation of children and child sex trafficking is a major public health issue globally. Domestic minor sex trafficking has become increasingly recognized within the United States. Sexually exploited minors are commonly identified as having psychosocial risk factors, including histories of abuse or neglect, running away, substance use or abuse, and involvement with child protective services. Youth also suffer a variety of physical and mental health consequences, including posttraumatic stress disorder, depression, anxiety, and suicidality. Child psychiatrists and other medical providers have the opportunity to identify, interact, and intervene on behalf of involved and at-risk youth.

Corrigendum: Clonal fate mapping quantifies the number of haematopoietic stem cells that arise during development

Corrigendum: Clonal fate mapping quantifies the number of haematopoietic stem cells that arise during development

Domestic Minor Sex Trafficking in the Medical Setting: A Survey of the Knowledge, Discomfort, and Training of Pediatric Attending Physicians

ABSTRACT Domestic minor sex trafficking (DMST) is a severe manifestation of sexual abuse and a major domestic health issue. The adverse health consequences of DMST bring victims into contact with health institutions and medical providers frequently, providing the opportunity for identification and intervention. Youth at risk or involved in DMST, however, are difficult to identify and often go unrecognized during health care visits. Little is known about the knowledge, comfort, and training gaps of physicians in identifying and managing patient victims of DMST. Our objectives were to assess (1) reported training and experiences; (2) perceived knowledge, comfort, and barriers; and (3) performance on medical decision-making questions regarding the identification, screening, and management of DMST in a population of pediatric attending physicians. An anonymous electronic survey was sent to pediatricians in Rhode Island from November 2014 through January 2015. Voluntary participants were 109 Rhode Island general pediatric and pediatric subspecialist physicians. Overall, participants perceived having limited knowledge, comfort, and training and reported barriers that corresponded with inaccurate answers on medical decision-making questions. These findings identify the impediments and obstacles to the care of DMST patients and inform the need for standardized education and training for pediatricians on this issue.

Abstract B035: CXCL8/CXCR1 signaling promotes angiogenesis and hematopoietic stem and progenitor cell function

CXCL8 (IL-8) is a chemokine with pleiotropic roles in host defense, angiogenesis and tumor metastasis. CXCL8 and its specific receptor, CXCR1, are broadly expressed within the hematopoietic and vascular systems. In an effort to identify novel secreted factors with effects on hematopoietic stem and progenitor cell (HSPC) function, we have recently identified CXCL8/CXCR1 signaling as a positive regulator of HSPC colonization of the zebrafish caudal hematopoietic territory (CHT). The CHT is a vascular niche that serves as the primary site of hematopoiesis from 36 hours post fertilization (hpf) to 6 days post fertilization (dpf). This observation raised the question whether CXCR1 signaling might induce dynamic changes in the CHT that favor HSPC colonization. CXCR1 was expressed at high levels in endothelial cells using a kdrl(VEGFR2):CXCR1;kdrl:mCherry double transgenic line. The CHT was imaged by fluorescence confocal microscopy, reconstructed in 3 dimensions and the volume measured using digital image analysis software. Overexpression of CXCR1 within the endothelial cells of these animals increased the volume of the CHT by 28% (p = 0.02). To understand how CXCR1 affects the dynamics of niche development, we globally overexpressed CXCR1 beginning at 36 hpf using a heat shock induction system and performed time lapse confocal microscopy from 52 to 72 hpf. This revealed that overexpression of CXCR1 consistently increased the CHT volume from 53 to 72 hpf compared to control (21% increase at 72 hpf, p = 0.004). These studies did not show whether CXCR1 acted directly on the vascular niche or whether CXCR1 expression in endothelial cells might induce expression of soluble factors or activate circulating cells that then cause expansion of the niche through indirect mechanisms. To address this, we created parabiotic zebrafish by fusing kdrl:mCherry embryos at 4 hpf. One half of each parabiotic animal was modified by DNA microinjection to globally overexpress CXCR1 or GFP as a control via heat shock induction at 36 and 48 hpf. The volume of the CHT was measured in each half of each parabiotic animal at 72 hpf. In control parabiotics overexpressing GFP, there was no difference in CHT volume between modified and unmodified sides of the organism. However, in parabiotics overexpressing CXCR1, the CHT of the modified side was 27% larger compared with the unmodified side (p = 0.012), consistent with our previous results and suggesting that CXCR1 acts directly on the niche in this system. We then asked whether this volume change could affect HSPC engraftment. Parabiotic animals were created using Runx1:mCherry embryos that carry an HSPC-specific reporter transgene as “donors” and WT embryos as “recipients”. The recipient niche was modified as before to overexpress CXCR1 or GFP as a control. At 72 hpf there was no difference in HSPC colonization of donor and recipient niches when the recipient niche expressed GFP. However, when the recipient niche expressed CXCR1, there was a significant increase in HSPC colonization of the recipient niche compared to the donor niche (11.4+/-2.4 vs 19.8+/-3.5 HSPCs per CHT, p = 0.02). Taken together, these results identify a novel role for CXCL8/CXCR1 signaling in angiogenesis and HSPC biology and they provide a new example of how innate immune signaling pathways are important for stem cell function. Administration of CXCL8 to hematopoietic stem cell transplant recipients may therefore improve HSPC engraftment and clinical outcomes in patients who are being treated for hematologic malignancies. Citation Format: Bradley W. Blaser, Jessica L. Moore, Elliott Hagedorn, Brian Li, Vera Binder, Owen Tamplin, Leonard I. Zon. CXCL8/CXCR1 signaling promotes angiogenesis and hematopoietic stem and progenitor cell function [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B035.